Overcharge protection device for a battery module

ABSTRACT

The present disclosure includes a battery module having a plurality of battery cells disposed in a housing. Each of the plurality of battery cells has a positive terminal, a negative terminal, an overcharge protection assembly, and a casing having an electrically conductive material. The overcharge protection assembly includes a vent, a first spring component, a second spring component, and an insulative component. The first spring component is coupled to the positive terminal, the second spring component is coupled to the negative terminal, the insulative component is between the first spring component and a conductive piece and between the second spring component and the conductive piece, and the vent is configured to drive the insulative component from between the first and second spring components and the conductive piece, such that the first and second spring components contact the conductive piece, when a pressure in the casing exceeds a threshold.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S.Provisional Application Ser. No. 62/031,729, entitled “EXTERNAL SHORTDEVICE FOR OVERCHARGE PROTECTION,” filed Jul. 31, 2014, which is herebyincorporated by reference.

BACKGROUND

The present disclosure relates generally to the field of batteries andbattery modules. More specifically, the present disclosure relates tofeatures of a battery cell that may protect a battery module fromthermal runaway during an overcharge event.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

A vehicle that uses one or more battery systems for providing all or aportion of the motive power for the vehicle can be referred to as anxEV, where the term “xEV” is defined herein to include all of thefollowing vehicles, or any variations or combinations thereof, that useelectric power for all or a portion of their vehicular motive force. Forexample, xEVs include electric vehicles (EVs) that utilize electricpower for all motive force. As will be appreciated by those skilled inthe art, hybrid electric vehicles (HEVs), also considered xEVs, combinean internal combustion engine propulsion system and a battery-poweredelectric propulsion system, such as 48 Volt (V) or 130V systems. Theterm HEV may include any variation of a hybrid electric vehicle. Forexample, full hybrid systems (FHEVs) may provide motive and otherelectrical power to the vehicle using one or more electric motors, usingonly an internal combustion engine, or using both. In contrast, mildhybrid systems (MHEVs) disable the internal combustion engine when thevehicle is idling and utilize a battery system to continue powering theair conditioning unit, radio, or other electronics, as well as torestart the engine when propulsion is desired. The mild hybrid systemmay also apply some level of power assist, during acceleration forexample, to supplement the internal combustion engine. Mild hybrids aretypically 96V to 130V and recover braking energy through a belt or crankintegrated starter generator. Further, a micro-hybrid electric vehicle(mHEV) also uses a “Stop-Start” system similar to the mild hybrids, butthe micro-hybrid systems of a mHEV may or may not supply power assist tothe internal combustion engine and operate at a voltage below 60V. Forthe purposes of the present discussion, it should be noted that mHEVstypically do not technically use electric power provided directly to thecrankshaft or transmission for any portion of the motive force of thevehicle, but an mHEV may still be considered an xEV since it does useelectric power to supplement a vehicle's power needs when the vehicle isidling with internal combustion engine disabled and recovers brakingenergy through an integrated starter generator. In addition, a plug-inelectric vehicle (PEV) is any vehicle that can be charged from anexternal source of electricity, such as wall sockets, and the energystored in the rechargeable battery packs drives, or contributes todrive, the wheels. PEVs are a subcategory of EVs that includeall-electric or battery electric vehicles (BEVs), plug-in hybridelectric vehicles (PHEVs), and electric vehicle conversions of hybridelectric vehicles and conventional internal combustion engine vehicles.

xEVs as described above may provide a number of advantages as comparedto more traditional gas-powered vehicles using only internal combustionengines and traditional electrical systems, which are typically 12Vsystems powered by a lead acid battery. For example, xEVs may producefewer undesirable emission products and may exhibit greater fuelefficiency as compared to traditional internal combustion vehicles and,in some cases, such xEVs may eliminate the use of gasoline entirely, asis the case of certain types of EVs or PEVs.

As technology continues to evolve, there is a need to provide improvedpower sources, particularly battery modules, for such vehicles. Forexample, battery modules may undergo overcharge testing to determineboundaries and/or limits of the battery module and its individualbattery cells. However, in certain instances, overcharging the batterymodule may lead to thermal runaway (e.g., an internal short circuit)caused by overheating or over pressurization of the battery cells.Thermal runaway may render the battery module permanently inoperable,and therefore, devices that may prevent or block thermal runaway aredesired.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

The present disclosure relates to a battery module having a housing anda plurality of battery cells disposed in the housing. Each of theplurality of battery cells has a positive terminal, a negative terminal,an overcharge protection assembly, and a casing having an electricallyconductive material. The overcharge protection assembly includes a vent,a first spring component, a second spring component, and an insulativecomponent. The first spring component is electrically coupled to thepositive terminal, the second spring component is electrically coupledto the negative terminal, the insulative component is disposed betweenthe first spring component and the casing and between the second springcomponent and the casing, and the vent is configured to drive theinsulative component from between the first and second spring componentsand the casing, such that the first and second spring componentselectrically contact the casing, when a pressure in the casing exceeds athreshold value.

The present disclosure also relates to a battery module that includes aplurality of battery cells disposed in a housing of the battery module.Each of the plurality of battery cells has a positive terminal, anegative terminal, an overcharge protection assembly, and a casing. Theovercharge protection assembly includes a vent, a first conductivecomponent, a second conductive component, and a conductive bistable arc,the first conductive component is electrically coupled to the positiveterminal, the second conductive component is electrically coupled to thenegative terminal, and the vent is configured to drive the conductivebistable arc into contact with both the first and second conductivecomponents when a pressure in the casing exceeds a threshold value.

The present disclosure also relates to a lithium-ion battery cell thatincludes a positive terminal, a negative terminal, a casing having anelectrically conductive material, and an overcharge protection assemblythat includes a vent flap, a first conductive component, a secondconductive component, and an insulating component. The vent flap has anopen position and a closed position, the first conductive component iselectrically coupled to the positive terminal, the second conductivecomponent is electrically coupled to the negative terminal, theinsulating component is positioned between the first conductivecomponent and the casing and between the second conductive component andthe casing when the vent flap is in the closed position, and the ventflap is configured to drive the insulating component from between thefirst conductive component and the casing and from between the secondconductive component and the casing when the vent flap moves from theclosed position to the open position, and the first and secondconductive components contact the casing when the vent flap is in theopen position.

DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a perspective view of a vehicle having a battery systemconfigured in accordance with present embodiments to provide power forvarious components of the vehicle;

FIG. 2 is a cutaway schematic view of an embodiment of the vehicle andthe battery system of FIG. 1;

FIG. 3 is a side view of a battery cell that includes an overchargeprotection assembly to prevent thermal runaway during an overchargetest, in accordance with an aspect of the present disclosure;

FIG. 4 illustrates a side view of the battery cell of FIG. 3 when a ventflap is in an open position, in accordance with an aspect of the presentdisclosure;

FIG. 5 illustrates an embodiment of a bus bar that includes twoconductive springs of the overcharge protection assembly of FIG. 3incorporated into a single piece, in accordance with an aspect of thepresent disclosure;

FIG. 6 illustrates another embodiment of an overcharge protectionassembly, in accordance with an aspect of the present disclosure;

FIG. 7 illustrates a perspective view of the battery cell and theovercharge protection assembly of FIG. 6, in accordance with an aspectof the present disclosure;

FIG. 8 illustrates another embodiment of an insulative component of theovercharge protection assembly of FIGS. 6 and 7, in accordance with anaspect of the present disclosure;

FIG. 9 illustrates another embodiment of the insulative component of theovercharge protection assembly of FIGS. 6-8, in accordance with anaspect of the present disclosure;

FIG. 10 illustrates a perspective view of the insulative component ofFIG. 9 in a first position, in accordance with an aspect of the presentdisclosure;

FIG. 11 illustrates another embodiment of an overcharge protectionassembly that may be utilized in a battery cell having a casing with aninsulative material, in accordance with an aspect of the presentdisclosure;

FIG. 12 illustrates a perspective view of the overcharge protectionassembly of FIG. 11, in accordance with an aspect of the presentdisclosure; and

FIG. 13 illustrates a graphical representation of data from anovercharge test performed on a battery cell utilizing an overchargeprotection assembly, in accordance with an aspect of the presentdisclosure.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

The battery systems described herein may be used to provide power tovarious types of electric vehicles (xEVs) and other high voltage energystorage/expending applications (e.g., electrical grid power storagesystems). Such battery systems may include one or more battery modules,each battery module having a number of battery cells (e.g., Lithium-ion(Li-ion) electrochemical cells) arranged to provide particular voltagesand/or currents useful to power, for example, one or more components ofan xEV. As another example, battery modules in accordance with presentembodiments may be incorporated with or provide power to stationarypower systems (e.g., non-automotive systems).

During the design and manufacturing process of a battery module, varioustests may be performed upon the battery module and its individualbattery cells to determine optimal performance parameters. For example,overcharge tests may provide excess electrical current to an individualbattery cell of a battery module using a power supply with a voltagethat exceeds a voltage of the individual battery cell. Overchargetesting may provide data related to temperature, heat output, and/orvoltage of the overcharged battery cell, which may enable designers ormanufacturers to modify various components of the battery cell toenhance performance (e.g., minimize damage to an overcharged batterycell). Therefore, such tests may be desirable for providing informationthat may enable manufacturers to optimize a battery module.

However, in certain cases, overcharging a battery cell may lead tothermal runaway (e.g., an internal short circuit) or another event thatcan permanently damage the battery cell. For instance, charging abattery cell may generate dendrites as a result of intercalation ofpositive ions in the anode. During an overcharge test, thermal runawaymay result due to an excess buildup of dendrites on a separator of abattery cell (e.g., the dendrites may penetrate the separator enablingmixing of the positive electrode and the negative electrode). Thermalrunaway may be undesirable because it generates excessive heat andpressure, which may cause permanent damage to the battery cell and/orrender the battery cell permanently inoperable.

It is now recognized that various features may be included in thebattery cell that prevent or block thermal runaway while performingovercharge tests. Some traditional battery cells may include a mechanismthat disrupts a flow of electrical current to at least one terminal ofthe battery cell when a pressure in the battery cell reaches a certainlevel. However, such mechanisms may ultimately lead to decreased currentcapacity of the battery cell. Therefore, it is now recognized that itmay be desirable to maintain the electrical connection to one or bothterminals of the battery cell while preventing thermal runaway duringovercharge. In accordance with aspects of the present disclosure, when apressure in the battery cell exceeds a threshold level, an externalshort circuit may be triggered by electrically coupling the positiveterminal and the negative terminal of the battery cell via a casing ofthe battery cell, for example. Accordingly, thermal runaway may beprevented and an electrical current capacity of the battery cellterminals is not reduced because the electrical pathway (e.g.,connection) from an external load to the terminals remains intact. Otherembodiments of the present disclosure include an overcharge protectionassembly that may trigger an external short circuit on a battery cellthat includes an electrically insulative casing.

Certain embodiments of the present disclosure relate to an overchargeprotection assembly for battery modules having battery cells withneutral cans. As used herein a “neutral can” may be defined as a batterycell casing that is not electrically coupled to either the positiveterminal or the negative terminal of the individual battery cell.Conversely, a “polarized can” may be defined as a battery cell casingwhich is electrically coupled to the positive terminal or the negativeterminal (e.g., the positive terminal or the negative terminal contactsthe battery cell casing) of the battery cell.

FIG. 1 is a perspective view of an embodiment of a vehicle 10, which mayutilize a regenerative braking system. Although the following discussionis presented in relation to vehicles with regenerative braking systems,the techniques described herein are adaptable to other vehicles thatcapture/store electrical energy with a battery, which may includeelectric-powered and gas-powered vehicles.

As discussed above, it would be desirable for a battery system 12 to belargely compatible with traditional vehicle designs. Accordingly, thebattery system 12 may be placed in a location in the vehicle 10 thatwould have housed a traditional battery system. For example, asillustrated, the vehicle 10 may include the battery system 12 positionedsimilarly to a lead-acid battery of a typical combustion-engine vehicle(e.g., under the hood of the vehicle 10). Furthermore, as will bedescribed in more detail below, the battery system 12 may be positionedto facilitate managing temperature of the battery system 12. Forexample, in some embodiments, positioning a battery system 12 under thehood of the vehicle 10 may enable an air duct to channel airflow overthe battery system 12 and cool the battery system 12.

A more detailed view of the battery system 12 is described in FIG. 2. Asdepicted, the battery system 12 includes an energy storage component 13coupled to an ignition system 14, an alternator 15, a vehicle console16, and optionally to an electric motor 17. Generally, the energystorage component 13 may capture/store electrical energy generated inthe vehicle 10 and output electrical energy to power electrical devicesin the vehicle 10.

In other words, the battery system 12 may supply power to components ofthe vehicle's electrical system, which may include radiator coolingfans, climate control systems, electric power steering systems, activesuspension systems, auto park systems, electric oil pumps, electricsuper/turbochargers, electric water pumps, heated windscreen/defrosters,window lift motors, vanity lights, tire pressure monitoring systems,sunroof motor controls, power seats, alarm systems, infotainmentsystems, navigation features, lane departure warning systems, electricparking brakes, external lights, or any combination thereof.Illustratively, in the depicted embodiment, the energy storage component13 supplies power to the vehicle console 16 and the ignition system 14,which may be used to start (e.g., crank) an internal combustion engine18.

Additionally, the energy storage component 13 may capture electricalenergy generated by the alternator 15 and/or the electric motor 17. Insome embodiments, the alternator 15 may generate electrical energy whilethe internal combustion engine 18 is running. More specifically, thealternator 15 may convert the mechanical energy produced by the rotationof the internal combustion engine 18 into electrical energy.Additionally or alternatively, when the vehicle 10 includes an electricmotor 17, the electric motor 17 may generate electrical energy byconverting mechanical energy produced by the movement of the vehicle 10(e.g., rotation of the wheels) into electrical energy. Thus, in someembodiments, the energy storage component 13 may capture electricalenergy generated by the alternator 15 and/or the electric motor 17during regenerative braking. As such, the alternator 15 and/or theelectric motor 17 are generally referred to herein as a regenerativebraking system.

To facilitate capturing and supplying electric energy, the energystorage component 13 may be electrically coupled to the vehicle'selectric system via a bus 19. For example, the bus 19 may enable theenergy storage component 13 to receive electrical energy generated bythe alternator 15 and/or the electric motor 17. Additionally, the bus 19may enable the energy storage component 13 to output electrical energyto the ignition system 14 and/or the vehicle console 16. Accordingly,when a 12 volt battery system 12 is used, the bus 19 may carryelectrical power typically between 8-18 volts.

Additionally, as depicted, the energy storage component 13 may includemultiple battery modules. For example, in the depicted embodiment, theenergy storage component 13 includes a lithium ion (e.g., a first)battery module 20 and a lead-acid (e.g., a second) battery module 22,which each includes one or more battery cells. In other embodiments, theenergy storage component 13 may include any number of battery modules.Additionally, although the lithium ion battery module 20 and lead-acidbattery module 22 are depicted adjacent to one another, they may bepositioned in different areas around the vehicle. For example, thelead-acid battery module 22 may be positioned in or about the interiorof the vehicle 10 while the lithium ion battery module 20 may bepositioned under the hood of the vehicle 10.

In some embodiments, the energy storage component 13 may includemultiple battery modules to utilize multiple different batterychemistries. For example, when the lithium ion battery module 20 isused, performance of the battery system 12 may be improved since thelithium ion battery chemistry generally has a higher coulombicefficiency and/or a higher power charge acceptance rate (e.g., highermaximum charge current or charge voltage) than the lead-acid batterychemistry. As such, the capture, storage, and/or distribution efficiencyof the battery system 12 may be improved.

To facilitate controlling the capturing and storing of electricalenergy, the battery system 12 may additionally include a control module24. More specifically, the control module 24 may control operations ofcomponents in the battery system 12, such as relays (e.g., switches)within energy storage component 13, the alternator 15, and/or theelectric motor 17. For example, the control module 24 may regulate anamount of electrical energy captured/supplied by each battery module 20or 22 (e.g., to de-rate and re-rate the battery system 12), perform loadbalancing between the battery modules 20 and 22, determine a state ofcharge of each battery module 20 or 22, determine temperature of eachbattery module 20 or 22, control voltage output by the alternator 15and/or the electric motor 17, and the like.

Accordingly, the control unit 24 may include one or more processors 26and one or more memory components 28. More specifically, the one or moreprocessors 26 may include one or more application specific integratedcircuits (ASICs), one or more field programmable gate arrays (FPGAs),one or more general purpose processors, or any combination thereof.Additionally, the one or more memory components 28 may include volatilememory, such as random access memory (RAM), and/or non-volatile memory,such as read-only memory (ROM), optical drives, hard disc drives, orsolid-state drives. In some embodiments, the control unit 24 may includeportions of a vehicle control unit (VCU) and/or a separate batterycontrol module.

As discussed above, before a battery module may be used to supply powerto an xEV, various tests may be conducted upon the battery module andits individual battery cells to optimize operating parameters of thebattery module. One such test may be an overcharge test that determineshow much electrical current a battery cell may receive, or how long abattery cell may receive an electrical current, before damage occurs tothe battery cell. However, in certain instances, overcharge tests mayresult in thermal runaway (e.g., an internal short circuit within thebattery cell), which may cause permanent damage to the battery cellbecause of excess heat and pressure generated from the overcharge. It isnow recognized that it may be desirable to prevent thermal runaway(e.g., an internal short circuit) by triggering an external shortcircuit (e.g., electrically coupling the positive terminal and thenegative terminal of the battery cell) before thermal runaway occurs. Incertain embodiments, the external short circuit may be triggered byestablishing an electrical connection between a positive terminal of abattery cell and a casing of the battery cell as well as between anegative terminal of the battery cell and the casing (e.g., can). Insome embodiments, a conductive component (e.g., a conductive piece),other than the battery cell casing, may be utilized to establish theelectrical connection. Accordingly, an electrical connection may beestablished between the positive cell and the negative cell, therebytriggering a short circuit.

FIG. 3 is a side view of a battery cell 50 that may include anovercharge protection assembly 52 to prevent thermal runaway duringovercharge tests. The battery cell 50 may be used in the lithium-ionbattery module 20 that supplies power to an xEV. It should be noted thatwhile the current discussion focuses on an overcharge protectionassembly in a lithium-ion battery cell 50, embodiments of the overchargeprotection assembly may be employed in any suitable battery cell thatundergoes overcharge tests.

As shown in the illustrated embodiment of FIG. 3, the battery cell 50includes a positive terminal 54 and a negative terminal 56. The batterycell 50 illustrated in FIG. 3 includes a neutral can (e.g., casing)because both the positive terminal 54 and the negative terminal 56 areelectrically insulated from a casing 58 of the battery cell 50 (e.g.,the casing 58 includes an electrically conductive material). In someembodiments, the casing 58 may be used to establish an electricalconnection between the positive terminal 54 and the negative terminal56, or a conductive piece attached to the battery cell 50 may be usedinstead of the casing 58 to form the electrical connection. In certainembodiments, the positive terminal 54 may include a first insulativegasket 60 configured to prevent electrical current from flowing from thepositive terminal 54 to the casing 58, or vice versa. Similarly, thenegative terminal 56 may include a second insulative gasket 62 thatprevents electrical current from flowing from the negative terminal 56to the casing 58, or vice versa. In some embodiments, a portion of thecasing 58 is non-conductive and prevents electrical current from flowingfrom the positive and negative terminals 54, 56 or to conductive partsof the casing 58. According, a conductive piece may be used to triggerthe external short circuit and to establish the electrical connectionbetween the positive and negative terminals 54, 56.

Additionally, the illustrated embodiment of FIG. 3 shows the overchargeprotection assembly 52 having a vent flap 64, a first conductive spring66, a second conductive spring 68, and an insulative component 70. Thefirst conductive spring 66 may be electrically coupled to the positiveterminal 54 and the second conductive spring 68 may be electricallycoupled to the negative terminal 56. In certain embodiments, the firstand second conductive springs 66, 68 may be disposed over the positiveand/or negative terminals 54, 56 via a hole or opening in the first andsecond conductive springs 66, 68 that is configured to receive thepositive and/or negative terminals 54, 56. Further, the first and secondconductive springs 66, 68 may be electrically coupled to the positiveand/or negative terminals 54, 56 via a weld (e.g., a laser weld). Inother embodiments, the first and second conductive springs 66, 68 may beelectrically coupled to the positive and/or negative terminals 54, 56via a fastener (e.g., screw or bolt). In still further embodiments, thefirst and second conductive springs 66, 68 may be electrically coupledto the positive and/or negative terminals 54, 56 using any suitabletechnique for establishing an electrical connection between the positiveand/or negative terminals 54, 56 and the first and second conductivesprings 66, 68.

Additionally, the first and second conductive springs 66, 68 may includea conductive metal (e.g., aluminum or copper) such that an electricalconnection may be established between the first conductive spring 66 andthe casing 58 and/or between the second conductive spring 68 and thecasing 58. The first and second conductive springs 66, 68 may be shapedin such a manner as to bias the first and second conductive springs 66,68 towards the casing 58. For example, when the first conductive spring66 is coupled to the positive terminal 54, a first recessed portion 72of the first conductive spring 66 may be driven towards the casing 58.When the first recessed portion 72 contacts the casing 58, an electricalconnection may be established between the positive terminal 54 and thecasing 58. Similarly, when the second conductive spring 68 is coupled tothe negative terminal 56, a second recessed portion 74 of the secondconductive spring 68 may be driven towards the casing 58. When thesecond recessed portion 74 contacts the casing 58, an electricalconnection may be established between the negative terminal 56 and thecasing 58. When both the first and second recessed portions 72, 74contact the casing 58, an electrical connection may be establishedbetween the positive terminal 54 and the negative terminal 56 via thecasing 58, which may trigger a short circuit.

However, it may be undesirable to trigger such a short circuit duringnormal operation of the battery cell 50 (e.g., when the battery cell 50is not overcharged). Therefore, when a pressure in the casing 58 of thebattery cell 50 is below the threshold value, it may be desirable toprevent formation of the electrical connection between the positiveterminal 54 and the negative terminal 56. Accordingly, to avoidestablishing such an electrical connection during normal operation ofthe battery cell 50 (e.g., when the pressure in the casing 58 is belowthe threshold value), the insulative component 70 may be disposedbetween the first recessed portion 72 of the first conductive spring 66and the casing 58. Similarly, the insulative component may be disposedbetween the second recessed portion 74 of the second conductive spring68 and the casing 58. In other embodiments, the insulative component 70may be disposed between first recessed portion 72 or the second recessedportion 74 and the casing 58. In still further embodiments, a secondinsulative component may be utilized such that the insulative component70 is disposed between the first recessed portion 72 and the casing 58,and the second insulative component may be disposed between the secondrecessed portion 74 and the casing 58.

In certain embodiments, the insulative component 70 and/or the secondinsulative component may include any material (e.g., plastic, ceramic,rubber, or another non-conductive material) that may be configured toprevent electrical current from flowing through the insulative component70 and/or the second insulative component. Therefore, during normaloperation of the battery cell 50, the insulative component 70 and/or thesecond insulative component may block formation of the electricalconnection between the positive terminal 54 and the negative terminal 56(e.g., via the first and/or second conductive springs 66, 68 and thecasing 58).

To produce electrical power in the battery cell 50, one or more chemicalreactions may take place. In some cases, such reactions form a gas(e.g., electrolyte) as a byproduct, and thus, the pressure within thecasing 58 increases as more gas is produced. As a battery isovercharged, a temperature within the casing 58 may increase (e.g., froman excess of electric current), which in turn, may further increase thepressure in the casing 58. In certain embodiments, the vent flap 64 maybe calibrated to open (e.g., from a pressure force within the casing 58)when the pressure within the casing 58 reaches a threshold value (e.g.,a predetermined pressure value lower than a pressure known to indicatethermal runaway). When the vent flap 64 opens, gas within the casing 58may escape (e.g., flow out of) into a housing of the battery module 20.

FIG. 4 illustrates a side view of the battery cell 50 when the vent flap64 is in an open position as a result of the pressure in the casing 58reaching the threshold value. When the pressure in the casing 58 reachesthe threshold value, the vent flap 64 may be configured to open as shownin FIG. 4. Accordingly, the vent flap 64 may be biased towards a closedposition (e.g., the position illustrated in FIG. 3), but when thepressure in the casing 58 reaches the threshold value, the pressureforce may be sufficient to overcome the bias and urge the vent flap 64to the open position (e.g., the position shown in FIG. 4).

In certain embodiments, the vent flap 64 may include a dual-doorconfiguration such that the vent flap 64 opens down a crease (e.g.,seam) in a center of the vent flap 64 (e.g., as if the vent flap 64 isconnected to the casing 58 via two hinges, one for each door). Forexample, the vent flap 64 may include an indented crease (e.g.,punctures in the vent flap that do not enable gas to pass out of thecasing 58) located in the center of the vent flap 64. Accordingly, whenthe pressure in the casing 58 reaches the threshold value, the indentedcrease may break (e.g., rupture) and enable two doors of the vent flap64 to open in a direction 76 to drive the insulative component 70 frombetween the first and/or second conductive springs 66, 68 and the casing58. The crease may be thinner than other parts of the casing 58 andhinges on either side of the crease may also be thinner than the casing58, but not as thin as the crease. In other embodiments, the vent flap64 may be configured to open as if connected to the casing 58 via asingle hinge (e.g., the vent flap 64 includes a single door). Forexample, the vent flap 64 may include a perimeter that includes anindented portion. Accordingly, when the pressure in the casing 58reaches the threshold value, the indented portion may break (e.g.,rupture) such that the entire vent flap 64 moves in the direction 76 todrive the insulative component 70 from beneath the first and/or secondconductive springs 66, 68. In still further embodiments, the vent flap64 may be configured to open in any suitable manner that may move theinsulative component 70 from between the first conductive spring 66 andthe casing 58 as well as from between the second conductive spring 68and the casing 58. In any event, when the vent flap 64 opens, the firstand second conductive springs 66, 68 may be configured to contact thecasing 58 and establish an electrical connection between the positiveterminal 54 and the negative terminal 56 via the casing 58.

Accordingly, when the pressure in the casing 58 reaches the thresholdvalue, the vent flap 64 may move to the open position (e.g., in thedirection 76) and move the insulative component 70 such that it nolonger is positioned between the first and second conductive springs 66,68 and the casing 58. When the insulative portion 70 is moved by thevent shield 64, the first and second conductive springs 66, 68 maycontact the casing 58 and establish an electrical connection between thepositive terminal 54 and the negative terminal 56, via the casing 58.The electrical connection may then cause a short circuit, which may leadto a discharge of electrical current from the cell 50. Additionally, theshort circuit may form an alternative path for charge current receivedfrom a power supply because a resistance of the short circuit may besubstantially smaller than an internal resistance of the cell 50. Suchan external short circuit may avoid thermal runaway within the batterycell 50 when the battery cell 50 is overcharged (e.g., during anovercharge test). The external short circuit may be triggered viacontact between the casing and the insulated positive and negativeterminals 54, 56. However, an electrical connection between the positiveand/or negative terminal 54, 56 and an external load (e.g., anotherbattery) is not disrupted (e.g., by breaking a connection between theterminal 54, 56 and the external load) by the external short circuit.Rather, electrical connections between the positive and/or negativeterminals 54, 56 are maintained (e.g., a current capacity of the batterycell 50 is not substantially affected), while the external short circuitserves to discharge the battery cell 50 and avoid thermal runaway.

In certain embodiments, more than one battery cell may be included inthe battery module 20. The power supplied by the battery module 20 maybe generated from each of the individual battery cells 50 included inthe battery module 20. Therefore, the battery cells 50 may be coupled toone another such that the power supplied by the battery module 20 iscumulative of a power associated with each of the individual batterycells 50. Accordingly, it may be desirable to incorporate conductivesprings into a bus bar that interconnects battery cells 50 in thebattery module 20 to simplify assembly and manufacturing of the batterymodule 20.

FIG. 5 illustrates an embodiment of a bus bar 90 that includes the firstconductive spring 66 and a third conductive spring 92 incorporated intoa single piece (e.g., the bus bar 90). In certain embodiments, the thirdconductive spring 92 may be disposed on a terminal 91 (e.g., a positiveterminal or a negative terminal) of a second battery cell 93 positionedadjacent to the battery cell 50. For example, the first conductivespring 66 may be coupled to the positive terminal 54 of the battery cell50. Additionally, the third conductive spring 92 may be coupled to theterminal 91 of the second battery cell 93. When the terminal 91 is apositive terminal, the battery cell 50 may be coupled to the secondbattery cell 93 in a parallel configuration via the bus bar 90.Connecting two battery cells 50, 93 in a parallel configuration may bedesirable because a parallel connection enables the battery module 20 tohave a voltage output equal to the sum of the individual battery cells50 connected in parallel. Conversely, when the terminal 91 is a negativeterminal of the second battery cell 93, the battery cell may be coupledto the second battery cell 93 in a series configuration via the bus bar90.

The first conductive spring 66 may be electrically coupled to thepositive terminal 54 or the negative terminal 56 of the battery cell 50.Similarly, the third conductive spring 92 may be electrically coupled tothe terminal 91 of the second battery cell 93, which may be eitherpositive or negative. In certain embodiments, the first conductivespring 66 may be disposed over a respective terminal 54, 56 via a firstopening 94 (e.g., a hole aligned with the respective terminal 54, 56) ofthe bus bar 90 configured to receive the positive and/or negativeterminals 54, 56. Similarly, the third conductive spring 92 may bedisposed over the terminal 91 via a second opening 96 (e.g., a holealigned with the terminal 91) of the bus bar 90 configured to receivethe terminal 91 of the second battery cell 93. Further, the first and/orthird conductive springs 66, 92 of the bus bar 90 may be electricallycoupled to respective terminals 54, 56, and/or 91 via a weld (e.g., alaser weld). In other embodiments, the first and third conductivesprings 66, 92 of the bus bar 90 may be electrically coupled to therespective terminals 54, 56, and/or 91 via a fastener (e.g., screw orbolt). In still further embodiments, the first and third conductivesprings 66, 92 of the bus bar 90 may be secured to the respectiveterminals 54, 56, and/or 91 using any suitable technique forestablishing an electrical connection between the respective terminals54, 56, and/or 91 and the first and third conductive springs 66, 92.

FIG. 6 illustrates another embodiment of the overcharge protectionassembly 52. As shown in the illustrated embodiment of FIG. 6 the firstand second conductive springs 66, 68 may not be directly coupled to thepositive terminal 54 and the negative terminal 56, respectively. Rather,intermediate components (e.g., terminal pads) may be directly coupled tothe terminals 54, 56, as well as to the first and second conductivesprings 66, 68. Therefore, a first terminal pad 100 may be coupled tothe positive terminal 54 at a first end 102 of the first terminal pad100 and to the first conductive spring 66 at a second end 104 of thefirst terminal pad 100. Similarly, a second terminal pad 106 may becoupled to the negative terminal 56 at a first end 108 of the secondterminal pad 106 and to the second conductive spring 68 at a second end110 of the second terminal pad 106. In certain embodiments, the terminalpads 100, 106 may include “Z”-shaped cross-sections. Accordingly, theterminal pads 100, 106 may be configured to couple two components thatare positioned on different planes (e.g., two components with differentheights). For example, the positive terminal has an end 112 that lies ona different plane than the first conductive spring 66 when it contactsthe casing 58. Therefore, the “Z” shape of the terminal pads 100, 106may enable such components to be electrically coupled to one another.

As shown in the illustrated embodiment of FIG. 6, the first terminal pad100 is coupled to the first conductive spring 66 via a TOX® joint, whichis a registered trademark of TOX® PRESSOTECHNIK L.L.C. Additionally, thesecond terminal pad 106 is coupled to the second conductive spring 68via a TOX® joint. A TOX® joint may be a joint between two componentsthat secures the two components together. Additionally, when the twocomponents include a conductive material, an electrical connection mayalso be established between the two components via the TOX® joint. Inother embodiments, the terminal pads 100, 106 may be coupled to theconductive springs 66, 68 via welding (e.g., laser welding) and/or afastener (e.g., rivets, screws, bolts).

Additionally, the terminal pads 100, 106 may be coupled to the terminals54, 56 via a weld (e.g., laser weld) such that the terminal pads 100,106 are secured to the terminals 54, 56 and form an electricalconnection between the terminal pads 100, 106 and the terminals 54, 56.In other embodiments, the terminal pads 100, 106 may be coupled to theterminals 54, 56 via fasteners (e.g., rivets, screws, or bolts), or anyother suitable technique for securing and electrically coupling twocomponents to one another.

In certain embodiments, the terminal pads 100, 106 and the conductivesprings 66, 68 may further be secured to the battery cell 50 via variousgrooves 114 (e.g., fabricated recesses or slots) within a separatecarrier device (e.g., a housing component coupled to the casing 58). Asshown in the illustrated embodiment of FIG. 6, the terminal pads 100,106 and the conductive springs 66, 68 may be substantially fixed withinthe grooves 114. The grooves 114 may prevent substantial movement of theterminal pads 100, 106 and/or the conductive springs 66, 68 due tomovement of the battery module 20 caused by the xEV, for example. Whenthe vent flap 64 opens, the insulative component 70 may be removed frombetween the first and second conductive springs 66, 68 and the casing 58such that the first and second conductive springs 66, 68 will bothcontact the casing 58 and trigger a short circuit.

FIG. 6 also illustrates another embodiment of the insulative component70. As shown, the insulative component 70 may include a first slot 116configured to be positioned between the casing 58 and the firstconductive spring 66 when the pressure within the casing 58 is below thethreshold value (e.g., the vent flap 64 is closed). Similarly, theinsulative component 70 may include a second slot 118 configured to bepositioned between the casing 58 and the second conductive spring 68when the pressure within the casing 58 is below the threshold value(e.g., the vent flap 64 is closed).

As discussed above, gas may be produced as a byproduct of the chemicalreactions taking place within the casing 58. Such gas may build upduring an overcharge test, thereby increasing the pressure in thecasing. In certain embodiments, when the pressure reaches or exceeds athreshold value, the vent flap 64 may be configured to open. Moreover,the pressure force applied to the vent flap 64 by the gas in the casing58 may further be utilized to remove the insulative component 70 frombetween the casing 58 and the first and second conductive springs 66,68. For example, when the vent flap 64 opens, doors of the vent flap 64may press against the insulative component 70 and drive the insulativecomponent 70 in a direction 120. Accordingly, the first slot 116 may beremoved from the position between the first conductive spring 66 and thecasing 58 and the second slot 118 may be removed from the positionbetween the second conductive spring 68 and the casing 58. Therefore,the first and second conductive springs 66, 68 may then contact thecasing 58, which may establish an electrical connection between thepositive terminal 54 and the negative terminal 56. Such an electricalconnection may trigger an external short circuit, which may dischargethe battery cell 50. It may be desirable to trigger the external shortcircuit before an internal short circuit (e.g., thermal runaway) occursbecause the internal short circuit (e.g., thermal runaway) may causepermanent damage to the battery cell 50 and/or render the battery cell50 inoperable.

FIG. 7 illustrates a perspective view of the battery cell 50 and theovercharge protection assembly 52 of FIG. 6. As can be seen in FIG. 7, aseparate carrier 130 is attached to the battery cell 50. The separatecarrier 130 may house the positive terminal 54, the negative terminal56, the first conductive spring 66, the second conductive spring 68, theinsulative component 70, as well as other components of the battery cell50 that may be positioned proximate to the vent flap 64. In certainembodiments, the separate carrier 130 may include an insulative material(e.g., a material that prevents or blocks electrical current fromflowing through it). For example, it may be desirable to utilize aninsulative material to construct the separate carrier 130 to avoidinadvertent short circuits (e.g., the separate carrier may block metalparticles from contacting the positive terminal 54 and/or the negativeterminal 56). Additionally, when both the first and second conductivesprings 66, 68 are housed within the separate carrier 130, a shortcircuit may be avoided even when the first and/or second conductivesprings 66, 68 contact the separate carrier 130.

In certain embodiments the separate carrier 130 may include protrusions132 that hold the insulative component 70 in place. For example, thebattery cell 50 may be disposed within the battery module 20, which maybe utilized to power an xEV. As the xEV moves, the xEV may subject thebattery module 20 to various vibrations and/or other disturbances thatmay cause the insulative component 70 to become misaligned with the ventflap 64. Accordingly, the protrusions 132 may provide a barrier tomovement of the insulative component 70 in the direction 120, such thatthe protrusions 132 may prevent the insulative component 70 fromenabling the first and second conductive springs 66, 68 to contact thecasing 58 inadvertently (e.g., due to a bump in the road or othervibration). It should be noted that the force applied by the vent flap64 to the insulative component 70 may be sufficient to move theinsulative component in the direction 120 past the protrusions 132. Theprotrusions 132 may therefore be configured to prevent the insulativecomponent 70 from moving in the direction 120 unless a sufficient forceis applied by the vent flap 64.

Additionally, FIG. 7 illustrates the insulative component 70 having anopening 134. In certain embodiments, the opening 134 may enable gas toflow from the casing 58 into the housing of the battery module 20 whenthe vent flap 64 is open. It should be noted that in other embodiments,the insulative component 70 may not include the opening 134. Forexample, when the insulative component 70 moves in the direction 120, agap may be formed between the vent flap 64 and the insulative component70. In such embodiments, the gap may be sufficient to enable gas to flowout of the casing 58, around the insulative component 70, and into thehousing of the battery module 20.

FIG. 8 illustrates another embodiment of the insulative component 70 ofFIGS. 6 and 7. In the illustrated embodiment of FIG. 8, the insulativecomponent 70 may include a length 140 and a width 142. The length 140and the width 142 of the insulative component 70 may be configured toensure that the insulative component 70 will move in the direction 120when the vent flap 64 opens. In certain embodiments, a smaller (e.g.,shorter length 140 and/or width 142) insulative component may facilitatemovement of the insulative component 70 in the direction 120 whencompared to a larger (e.g., longer length 140 and/or width 142)insulative component subjected to the same force. Therefore, in certainembodiments, shortening the width 142 of the insulative component 70 maybe desirable.

As shown in the illustrated embodiment of FIG. 8, the separate carrier130 coupled to the battery cell 50 may include a narrow portion 144. Thenarrow portion 144 may be adjacent to the vent flap 64 such that thenarrow portion 144 of the separate carrier 130 houses just theinsulative component 70. The narrow portion 144 may be desirable whenthe insulative component 70 may include a shorter width 142. Forexample, the narrow portion 144 may enable the smaller insulativecomponent 70 to be secured by the separate carrier 130, while othercomponents of the battery cell 50 may remain a standard size (e.g.,other battery cell components are not modified). Accordingly, theembodiment of FIG. 8 may enable the insulative component 70 to move inthe direction 120 when a smaller force is applied to the insulativecomponent 70 by the vent flap 64.

FIG. 9 illustrates another embodiment of the insulative component 70 ofthe overcharge protection assembly 52 of FIGS. 6-8. The illustratedembodiment of FIG. 9 shows that the insulative component 70 includes afirst insulative member 160, a second insulative member 162, and aninsulative bistable beam 164. In certain embodiments, the insulativebistable beam 164 may be incorporated into the separate carrier 130 ofthe battery cell 50. In other embodiments, the insulative bistable beam164 may be a separate component of the separate carrier 130.

As used herein, the insulative bistable beam 164 may be a component thatincludes a first position 166 and a second position 168. To transitionfrom the first position 166 to the second position 168 a force may beexerted upon the insulative bistable beam 164, which then causes thetransition. For example, during normal operation of the battery cell 50(e.g., when the pressure in the casing 58 is below the threshold value),the insulative bistable beam 164 may be in the first position 166. Theinsulative bistable beam 164 may be configured to remain in the firstposition 166 until a force from the vent flap 64 acts upon theinsulative bistable beam 164, thereby driving the insulative bistablebeam 164 to the second position 168. Accordingly, the insulativebistable beam 164 may be configured to withstand outside forces actingupon the battery module 20 caused by movement of the xEV, for example.In certain embodiments, once the insulative bistable beam 164 reachesthe second position 168, the insulative bistable beam 164 may not beconfigured to return to the first position 166 (e.g., the transitionfrom the first position 166 to the second position 168 is irreversible).

The first insulative member 160 and the second insulative member 162 maybe coupled to the insulative bistable beam 164. In certain embodiments,the insulative bistable beam 164 may include grooves 169 configured toreceive the first and second insulative members 160, 162. Further, thefirst and second insulative members 160, 162 may be secured in thegrooves 169 via an adhesive (e.g., glue, epoxy, or tape), via a fastener(e.g., a screw, a bolt, or a rivet), or via a heat seal. In otherembodiments, the first and second insulative members 160, 162 may beconfigured to couple to the insulative bistable beam 164 using anysuitable technique.

As shown in the illustrated embodiment of FIG. 9, the first insulativemember 160 is disposed between the first conductive spring 66 and thecasing 58 when the insulative bistable beam 164 is in the first position166. Similarly, the second insulative member 162 is disposed between thesecond conductive spring 68 and the casing 58 when the insulativebistable beam 164 is in the first position 166. When the pressure withinthe casing 58 reaches the threshold level, the vent flap 64 may open,which may then apply a force to the insulative bistable beam 164 causingthe insulative bistable beam 164 to move in the direction 120 from thefirst position 166 to the second position 168. Accordingly, when theinsulative bistable beam 164 moves towards the second position 168, theinsulative bistable beam 164 may pull the first and second insulativemembers 160, 162 out from between the first and second conductivesprings 66, 68 and the casing 58. The first and second conductivesprings 66, 68 may then contact the casing 58, thereby establishing anelectrical connection between the positive terminal 54 and the negativeterminal 56. Establishing such an electrical connection may trigger anexternal short circuit, which may discharge the battery cell 50 andprevent thermal runaway during an overcharge test.

In still further embodiments, the insulative component 70 may includethe insulative bistable beam 164 and a single insulative member.Accordingly, the single insulative member may be coupled to theinsulative bistable beam 164. When the insulative bistable beam 164 isin the first position 166, the single insulative member may be disposedbetween the first conductive spring 66 and the casing 58 and between thesecond conductive spring 68 and the casing 58. Conversely, when theinsulative bistable beam 164 moves to the second position 168, thesingle insulative member may be pulled by the bistable beam 164 frombetween the first conductive spring 66 and the casing 58 and frombetween the second conductive spring 68 and the casing 58. In suchembodiments that include the single insulative member, the groove 169may serve as a hinge joint to secure the single insulative member to theinsulative bistable beam 164 and to facilitate the insulative bistablebeam's 164 transition between positions 166 and 168.

FIG. 10 illustrates a perspective view of the insulative component 70 ofFIG. 9 in the first position 166. For example, the insulative bistablebeam 164 may include a first arm 170, a second arm 172, and an elbow174, where the elbow 174 connects the first arm 170 and the second arm172 to one another. As the insulative bistable beam 164 moves from thefirst position 166 to the second position 168, the elbow moves in thedirection 120. In certain embodiments, the elbow 174 may be at a lowestposition with respect to the arms 170, 172 when the insulative bistablebeam 164 is in the first position 166, and the elbow 174 may be at ahighest position with respect to the arms 170, 172 when the insulativebistable beam 164 is in the second position 168. As illustrated in theembodiment of FIG. 10, the elbow 174 is at the lowest point with respectto the arms 170, 172, and thus, is in the first position 166. When thepressure in the casing 58 reaches the threshold level, the vent flap 64may open and drive the insulative bistable beam 164 to the secondposition 168. Accordingly, the elbow 174 may transition to the highestposition with respect to the arms 170, 172 upon reaching the secondposition 168.

FIG. 11 illustrates another embodiment of the overcharge protectionassembly 52 that may utilize a casing 58 having an insulative material(e.g., a material that prevents electrical current from readily flowingthrough it). In regards to the discussion related to FIGS. 3-10, thecasing 58 included an electrically conductive material to establish theelectric pathway between the positive terminal 54 and the negativeterminal 56 when the conductive springs 66, 68 contacted the casing 58.However, in the illustrated embodiment of FIG. 11, the casing 58 mayinclude an electrically insulative material and the overchargeprotection assembly 52 may still create an external short circuit toprevent thermal runaway during an overcharge test.

For example, the overcharge protection assembly 52 of FIG. 11 mayinclude a conductive bistable arc 190. Additionally, the separatecarrier 130 (e.g., the separate carrier 130 including insulativematerial) may include a first notch 192 and a second notch 194configured to retain the conductive bistable arc 190 in a first position196 when the pressure in the casing 58 is below the threshold value. Forexample, a first end 198 of the conductive bistable arc 190 may bedisposed in the first notch 192 and a second end 200 of the conductivebistable arc 190 may be disposed in the second notch 194. In certainembodiments, the first notch 192 may also provide support for the firstconductive spring 66 (e.g., secure the first conductive spring 66 suchthat it remains substantially stationary with respect to the separatecarrier 130). Similarly, the second notch 194 may provide support forthe second conductive spring 68 (e.g., secure the second conductivespring 68 such that it remains substantially stationary with respect tothe separate carrier 130).

It should be noted that the separate carrier 130, as well as the firstnotch 192 and the second notch 194 may include an insulative material.Therefore, an electrical connection is absent between the conductivebistable arc 190 and the first and second conductive springs 66, 68 whenthe pressure in the casing 58 is below the threshold value.

In certain embodiments, the conductive bistable arc 190 may beconfigured to contact the vent flap 64 when the conductive bistable arc190 is in the first position 196. In other embodiments, a gap may beformed between the conductive bistable arc 190 and the vent flap 64 whenthe conductive bistable arc 190 is in the first position 196. In anyevent, the vent flap 64 may be configured to apply a force to theconductive bistable arc 190 when the vent flap 64 opens (e.g., as aresult of the pressure in the casing 58 reaching or exceeding thethreshold value) and drive the conductive bistable arc 190 to a secondposition 202.

As shown in the illustrated embodiment of FIG. 11, the first and secondconductive springs 66, 68 may be substantially straight (e.g., parallelto the casing 58). Therefore, the first and second conductive springs66, 68 may not be biased towards a surface of the casing 58 in theillustrated embodiment of FIG. 11. Rather, the first and secondconductive springs 66, 68 may be positioned in such a manner as toenable the conductive bistable arc 190 to contact both the firstconductive spring 66 and the second conductive spring 68 when theconductive bistable arc 190 is in the second position 202. Accordingly,when the conductive bistable arc 190 is in the second position 202, theconductive bistable arc 190 forms the electrical connection between thefirst conductive spring 66 and the second conductive spring 68 (e.g., asopposed to the casing 58 in the embodiments illustrated in FIGS. 3-10).Therefore, when the conductive bistable arc 190 is in the secondposition 202, an electrical connection is established between thepositive terminal 54 and the negative terminal 56 via the first andsecond conductive springs 66, 68 as well as the conductive bistable arc190.

In the embodiment illustrated in FIG. 11, the casing 58 is not utilizedto establish the electrical connection between the positive terminal 54and the negative terminal 56. Therefore, the casing 58 may include aninsulative material, while the external short circuit is still formed(e.g., via the conductive bistable arc 190) to prevent thermal runawayduring an overcharge test. Moreover, an electrical connection betweenthe positive terminal 54 and/or the negative terminal 56 and an externalload is not disrupted. Accordingly, the battery cell 50 may avoidthermal runaway while also maintaining a current capacity level (e.g.,the current capacity may not decrease).

FIG. 12 illustrates a perspective view of the overcharge protectionassembly 52 of FIG. 11. As shown in FIG. 12, the conductive bistable arc190 is in the first position 196 because the conductive bistable arc 190is concave with respect to the casing 58. Conversely, when theconductive bistable arc 190 is in the second position 202, theconductive bistable arc 190 may be convex with respect to the casing 58.

FIG. 13 illustrates a graphical representation 220 of data from anovercharge test performed on a battery cell utilizing the overchargeprotection assembly 52 of the present disclosure. The graph 220 shows anexample of an effect of the overcharge protection assembly 52 on abattery cell during an overcharge test. The graph 220 includes a firstcurve 222 representing voltage 224 as a function of state of charge(SOC) 226 for a battery cell that includes the overcharge protectionassembly 52. The first curve 222 shows how voltage 224 generallyincreases as SOC 226 increases for the battery cell including theovercharge protection assembly 52. However, as SOC 226 continues toincrease, the pressure in the casing 58 of the battery cell alsoincreases. As shown in the illustrated embodiment of FIG. 13, when thepressure reaches the threshold value, the overcharge protection assembly52 triggers an external short circuit by creating an electricalconnection between the positive terminal 54 and the negative terminal 56(e.g., via the casing 58 or the conductive bistable arc 190). Therefore,at point 228, the short circuit occurs and the voltage 224 of thebattery cell decreases significantly. Accordingly, the battery cell 50discharges, thereby preventing thermal runaway.

Conversely, a second curve 230 shows an effect on a battery cell thatdoes not include the overcharge protection assembly 52 of the presentdisclosure. Accordingly, the voltage 224 continues to increase beyondthe point 228 as the SOC 226 increases. Eventually, thermal runawayoccurs. Additionally, graph 220 illustrates a third curve 234representing a temperature 236 as a function of SOC 226 for a batterycell that includes the overcharge protection assembly 52. As shown, thetemperature 236 also increases as SOC 226 increases. Additionally, atthe point 228 (e.g., when the external short circuit is triggered), thetemperature 236 continues to increase. However, the temperature 236 doesincur a significant spike. Rather, the temperature 236 increases to amaximum point, but eventually decreases. Accordingly, thermal runawaydoes not occur.

Conversely, a fourth curve 238 illustrates the temperature 236 of abattery cell that does not include the overcharge protection assembly52. As shown, the temperature 236 incurs a large increase where thevoltage 224 spikes as a result of thermal runaway. Accordingly, theexcessive temperature experienced by the battery cell may createpermanent damage to the battery cell. Therefore, it is now recognizedthat the overcharge protection assembly 52 of the present disclosure mayprevent thermal runaway and may prevent permanent damage to the batterycell.

One or more of the disclosed embodiments, alone or in combination, mayprovide one or more technical effects useful in the manufacture ofbattery modules, and portions of battery modules. The disclosedembodiments relate to battery cells that include an overchargeprotection assembly. The overcharge protection assembly may include avent that opens (e.g., transitions from a first position to a secondposition) when a pressure in a casing of the battery cell reaches athreshold value. Accordingly, the opening of the vent may enableelectrical contact between a positive terminal and the battery cellcasing as well as a negative terminal and the battery cell casing.Accordingly, an external short circuit may be triggered by electricallycoupling the positive terminal and the negative terminal of the batterycell via the casing. Such an external short circuit may discharge thebattery cell, but the external short circuit may prevent thermal runawayand/or permanent damage to the battery cell. Moreover, such an externalshort circuit may be triggered without disrupting electrical currentfrom an external load to the positive and/or negative terminals.Therefore, a current capacity of the battery cell may be maintained(e.g., not decrease). It should be noted that the embodiments describedin the specification may have other technical effects and can solveother technical problems.

The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover all modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

1. A battery module, comprising: a housing; and a plurality of batterycells disposed in the housing, wherein each of the plurality of batterycells comprises a positive terminal, a negative terminal, an overchargeprotection assembly, and a casing comprising an electrically conductivematerial; wherein the overcharge protection assembly comprises a vent, afirst spring component, a second spring component, and an insulativecomponent, wherein the first spring component is electrically coupled tothe positive terminal, the second spring component is electricallycoupled to the negative terminal, the insulative component is disposedbetween the first spring component and a conductive piece and betweenthe second spring component and the conductive piece, and the vent isconfigured to drive the insulative component from between the firstspring component and the conductive piece and drive the insulativecomponent from between the second spring component and the conductivepiece, such that the first spring component and the second springcomponent each electrically contact the conductive piece, when apressure in the casing exceeds a threshold value.
 2. The battery moduleof claim 1, wherein the casing comprises the conductive piece.
 3. Thebattery module of claim 1, wherein at least one of the first springcomponent and the second spring component are integrated into a bus barconfigured to couple a first battery cell of the plurality of batterycells to a second battery cell of the plurality of battery cells.
 4. Thebattery module of claim 3, wherein the bus bar is coupled to a positiveterminal of the first battery cell of the plurality of battery cells andto a negative terminal of the second battery cell of the plurality ofbattery cells.
 5. The battery module of claim 3, wherein the bus bar iscoupled to a positive terminal of the first battery cell of theplurality of battery cells and to a positive terminal of the secondbattery cell of the plurality of battery cells.
 6. The battery module ofclaim 1, wherein the insulative component comprises a first slotconfigured to be positioned between the first spring component and theconductive piece and a second slot configured to be positioned betweenthe second spring component and the conductive piece.
 7. The batterymodule of claim 6, comprising a separate carrier coupled to the casing,and wherein the insulative component is disposed in the separatecarrier.
 8. The battery module of claim 7, wherein the separate carriercomprises a narrow section configured to receive the insulativecomponent, and wherein the insulative component comprises a width thatis narrower than a width of the casing.
 9. The battery module of claim1, wherein the insulative component comprises plastic, ceramic, rubber,nylon, or any combination thereof.
 10. The battery module of claim 1,wherein the insulative component comprises an insulative bistable beam,a first insulative member, and a second insulative member, theinsulative bistable beam is configured to be stable in a first positionand a second position, the first insulative member is configured to bepositioned between the first spring component and the conductive piecewhen the insulative bistable beam is in the first position, and thesecond insulative member is configured to be positioned between thesecond spring component and the conductive piece when the insulativebistable beam is in the first position.
 11. The battery module of claim10, wherein the first insulative member is coupled to the insulativebistable beam via a first groove and the second insulative member iscoupled to the insulative bistable beam via a second groove.
 12. Thebattery module of claim 11, wherein the insulative bistable beam isconfigured to pull the first insulative member from between the firstspring component and the conductive piece and to pull the secondinsulative member from between the second spring component and theconductive piece when the insulative bistable beam moves from the firstposition to the second position.
 13. The battery module of claim 1,comprising a first terminal pad and a second terminal pad.
 14. Thebattery module of claim 13, wherein a first end of the first terminalpad is directly coupled to the positive terminal and a second end of thefirst terminal pad is directly coupled to the first spring component,and wherein a third end of the second terminal pad is directly coupledto the negative terminal and a fourth end of the second terminal pad isdirectly coupled to the second spring component.
 15. A battery module,comprising: a plurality of battery cells disposed in a housing of thebattery module, wherein each of the plurality of battery cells comprisesa positive terminal, a negative terminal, an overcharge protectionassembly, and a casing; wherein the overcharge protection assemblycomprises a vent, a first conductive component, a second conductivecomponent, and a conductive bistable arc, the first conductive componentis electrically coupled to the positive terminal, the second conductivecomponent is electrically coupled to the negative terminal, and the ventis configured to drive the conductive bistable arc into contact withboth the first and second conductive components when a pressure in thecasing exceeds a threshold value.
 16. The battery module of claim 15,wherein the casing comprises an electrically insulative material. 17.The battery module of claim 15, wherein the conductive bistable arccomprises a first position and a second position, the conductivebistable arc is in the first position when the pressure in the casing isat or below the threshold value, and the conductive bistable arc isdriven to the second position by the vent when the pressure in thecasing exceeds the threshold value.
 18. The battery module of claim 17,wherein the conductive bistable arc is secured in the first position bya first notch and a second notch, and wherein the first notch and thesecond notch each comprise an insulative material.
 19. The batterymodule of claim 18, wherein the first and second notches are configuredto support the first conductive component and the second conductivecomponent, and the first and second notches are configured to preventelectrical contact between the conductive bistable arc and the first andsecond conductive components when the conductive bistable arc is in thefirst position.
 20. The battery module of claim 15, wherein theconductive bistable arc comprises aluminum.
 21. A lithium ion batterycell, comprising: a positive terminal; a negative terminal; a casinghaving an electrically conductive material; and an overcharge protectionassembly comprising a vent flap, a first conductive component, a secondconductive component, and an insulating component; wherein the vent flapis configured to transition from an open position to a closed position,the first conductive component is electrically coupled to the positiveterminal, the second conductive component is electrically coupled to thenegative terminal, the insulating component is positioned between thefirst conductive component and the casing and between the secondconductive component and the casing when the vent flap is in the closedposition, and the vent flap is configured to drive the insulatingcomponent from between the first conductive component and the casing andto drive the insulating component from between the second conductivecomponent and the casing when the vent flap moves from the closedposition to the open position, and the first and second conductivecomponents contact the casing when the vent flap is in the openposition.
 22. The lithium ion battery cell of claim 21, wherein the ventflap comprises an indented seam in a center of the vent flap, andwherein the indented seam is configured to break when a pressure in thecasing reaches a threshold value.
 23. The lithium ion battery cell ofclaim 21, wherein the vent flap comprises an indented portion on aperimeter of the vent flap, and wherein the indented portion isconfigured to break when a pressure in the casing reaches a thresholdvalue.
 24. The lithium ion battery cell of claim 21, wherein the firstconductive component is coupled to the positive terminal and the secondconductive component is coupled to the negative terminal via a weld. 25.The lithium ion battery cell of claim 21, wherein the first conductivecomponent is coupled to the positive terminal and the second conductivecomponent is coupled to the negative terminal via a fastener.